Monday, November 4, 2013

Soil pollution - Types, effects, sources and control of soil pollution

Soil pollution
Soil pollution is defined as, “contamination of soil by human and natural activities which may cause harmful effect on living organisms”. Composition of soil is listed below:
Organic mineral matter 45
Organic matter 05
Soil water 25
Soil air 25

Soil pollution mainly occurs due to the following:
  1. Industrial wastes
  2. Urban wastes
  3. Agricultural practices
  4. Radioactive pollutants
  5. Biological agents

Industrial wastes – Disposal of Industrial wastes is the major problem for soil pollution
Sources: Industrial pollutants are mainly discharged from various origins such as pulp and paper mills, chemical fertilizers, oil refineries, sugar factories, tanneries, textiles, steel, distilleries, fertilizers, pesticides, coal and mineral mining industries, drugs, glass, cement, petroleum and engineering industries etc.
Effect: These pollutants affect and alter the chemical and biological properties of soil. As a result, hazardous chemicals can enter into human food chain from the soil or water, disturb the biochemical process and finally lead to serious effects on living organisms.

Urban wastes – Urban wastes comprise of both commercial and domestic wastes consisting of dried sludge and sewage. All the urban solid wastes are commonly referred to as refuse.
Constituents of urban refuse: This refuse consists of garbage and rubbish materials like plastics, glasses, metallic cans, fibres, paper, rubbers, street sweepings, fuel residues, leaves, containers, abandoned vehicles and other discarded manufactured products. Urban domestic wastes though disposed off separately from industrial wastes, can still be dangerous. This happens because they are not easily degraded.

Agricultural practices – Modern agricultural practices pollute the soil to a large extent. With the advancing agro-technology, huge quantities of fertilizers, pesticides, herbicides and weedicides are added to increase the crop yield. Apart from these farm wastes, manure, slurry, debris, soil erosion containing mostly inorganic chemicals are reported to cause soil pollution

Radioactive pollutants/ - Radioactive substances resulting from explosions of nuclear testing laboratories and industries giving rise to nuclear dust radioactive wastes, penetrate the soil and accumulate giving rise to land/soil pollution.
  1. Radio nuclides of Radium, Thorium, Uranium, isotopes of Potassium (K-40) and Carbon (C-14) are commonly found in soil, rock, water and air.
  2. Explosion of hydrogen weapons and cosmic radiations include neutron, proton reactions by which Nitrogen (N-15) produces C-14. This C-14 participates in Carbon metabolism of plants which is then into animals and human beings.
  3. Radioactive waste contains several radio nuclides such as Strontium90, Iodine-129, Cesium-137 and isotopes of Iron which are most injurious. Strontium get deposited in bones and tissues instead of calcium.
  4. Nuclear reactors produce waste containing Ruthenium-106, Iodine-131, Barium-140, Cesium-144 and Lanthanum-140 along with primary nuclides Sr-90 with a half life 28 years and Cs-137 with a half life 30 years. Rain water carries Sr-90 and Cs-137 to be deposited on the soil where they are held firmly with the soil particles by electrostatic forces. All the radio nuclides deposited on the soil emit gamma radiations.
  5. Biological agents – Soil gets a large amount of human, animal and bird excreta which constitute a major source of land pollution by biological agents.
    Ex: 1. Heavy application of manures and digested sludge can cause serious damage to plants within a few years

Control measures of soil pollution:
  1. Soil erosion can be controlled by a variety of forestry and farm practices.
    Ex: Planting trees on barren slopes
      Contour cultivation and strip cropping may be practiced instead of shifting cultivation
      Terracing and building diversion channels may be undertaken.
Reducing deforestation and substituting chemical manures by animal wastes also helps arrest soil erosion in the long term.

    1. Proper dumping of unwanted materials: Excess wastes by man and animals pose a disposal problem. Open dumping is the most commonly practiced technique. Nowadays, controlled tipping is followed for solid waste disposal. The surface so obtained is used for housing or sports field.
    2. Production of natural fertilizers: Bio-pesticides should be used in place of toxic chemical pesticides. Organic fertilizers should be used in place of synthesized chemical fertilizers. Ex: Organic wastes in animal dung may be used to prepare compost manure instead of throwing them wastefully and polluting the soil.
    3. Proper hygienic condition: People should be trained regarding sanitary habits.
      Ex: Lavatories should be equipped with quick and effective disposal methods.
    4. Public awareness: Informal and formal public awareness programs should be imparted to educate people on health hazards by environmental education.
      Ex: Mass media, Educational institutions and voluntary agencies can achieve this.
    5. Recycling and Reuse of wastes: To minimize soil pollution, the wastes such as paper, plastics, metals, glasses, organics, petroleum products and industrial effluents etc should be recycled and reused.
      Ex: Industrial wastes should be properly treated at source. Integrated waste treatment methods should be adopted.
    6. Ban on Toxic chemicals: Ban should be imposed on chemicals and pesticides like DDT, BHC, etc which are fatal to plants and animals. Nuclear explosions and improper disposal of radioactive wastes should be banned.

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